Morton, Adam
Blackwell, 1997
Buku Teks SO
O`Brien, Dan
Polity Press, 2006
Buku Teks
Chisholm, Roderick M.
Prentice-Hall International, 1989
Buku Teks SO
Rescher, Nicholas
State University of New York Press, 2003
Buku Teks SO
Wojciechowski, Jerzy A.
Council for research in values and philosophy, [Date of publication not identified]
Buku Teks SO